Grinding wheel



Sept. 15, 1953 E; o. TEAGUE 2,652,320 GRINDING WHEEL Original Filed Sept. 7. 1950 J l l2 1/ '20 Inventor E R'NES T D nus 1 A 5 TE A G'LJE B y FTTOR'NEY Patented Sept. 15, 1953 fil lilCEv GRINDING WHEEL Ernest Douglas a ue, el n G rd n. ty

Englaniassignor to Norton Company,"Worcester,

ass., a corporation of Massachusetts Originalapplioation September 7., 1950, Serial No. 183,552, now Patent No. 2,624,650, dated Jami: ary 6, 1953. Divided; and this application September 2 1952,, Serial No. 307,4 7

4 Claims. 1.

The invention relates to. grinding wheels particularly to that variety thereof known as cop.- ing wheels, which are used to cut stone and other hard non-metallic materials. This application is a division of my copendingapplication Serial No. 1 3,552; filed September 7,. 1950, now Patent 2,624,660

One object of the invention is to provide a superior coping wheel. Another object of the invention is to provide a coping wheel which can be used dry grinding operations and which Will cut at a high rate without fracturing. Another object of the invention is to provide a coping wheel which can be used under conditions which will malge it veryhot without fracturing. Another obj ct of the invention is to provide a coping wheel which can be used under such conditions that it becomes very hot and which nevertheless has a high rate of cut and relatively low wheel wear.

Other objects will be in part obvious or in part pointed out hereinaiter.

In the accompanying drawings illustrating two of many possible embodiments of the mechanical features of this invention,

Figure l is, a side elevation of a typical steel center for a coping wheel, the boundaries of the abrasive material to be molded thereon being indicated by dotted lines,

Figure 2 is a fragmentary diametral cross-sectional view on a lar er scale than Figure 1 ofa coping wheel constructed in accordance with the invention,

Figure 3- is a cross-sectional view similar to Figure 2 illustrating another embodiment of the invention.

For the manufacture of a coping wheel in accordance with the invention, I provide a steel center such as the steel center ID. This steel center [6 as illustrated in Figure 1 is a typical shape ,ofsteel center for coping wheels, the shape in cross section of the peripheral portion being shown in Figures 2 and 3. This steel center l has cut-outs II at the periphery thereof for ning a plurality of peripheral dovetails l2. Desirably also a plurality of holes l3 are provided in the peripheral portion [4 in which the dovetails l2 are formed; this peripheral portion I4 is separated from the hub portion l5 by means of shoulders l6, one on each side of the center Hi The hub portion I5 has a central hole I! so that the center can be mounted upon a spindle. The sides of the hub portion I5 may be plane parallel surfaces and the sides of the peripheral portion l4 may also be plane parallel surfaces.

irreversible condition.

The section planes of Figures 2 and 3 are not taken through, thout-outslf or holes [3. The o e oin de qipfi 9 t te e t n is lustrative and other shapes and styles of steel centers may be used in accordance with this invention, It will be seen that the steel center I0 is essentially a discmodified by the features above described.

On the steel center It] is molded an annular portion 20 of abrasive and phenolic resin bond. This annular portion 20, is continuous around the entire steel center Ill and interlocks with the dovetails l2 and holes it. Between the steel cen ter Ill and the annular portionjfZO is a layerZlq of thermoplastic resin as shown in Figure 2 or a er 2 thexmp lasti e n nc i anular, reiractory or abrasive material, as shown in Figure 3.

The abrasive materialin the anm lar portion 2] is preferably silicon carbide abrasive since this br i Preferred, is? he r i din most n s u h s r nite marble o th ik the grinding. Q 191, 9? am nQH' 1 materials such a porcelain, glass and concrete. However, within the scope pi the invention other abrasives a e u uch a alumi um oxid abrasive including the product of the electric furnace or natural corundum or emery.

The bond in the annular portion 20 is a phenol formaldehyde resin of any desired variety. Commercial resins usually contain a minor proportion of cresol formaldehyde and snch resin can be used advantageously in this invention. Furthermore I use the word phenol in the broad sense to include phenolic bodies such as cresol and xylenol. These, as well as phenol in the stricter sense, comprise a benzene ring with an OH group thereon. In making up th mixture f urfural can be used as a plasticizer in which case there Will result some furyl methylene linkages as well as methylene linkages. The uncured resin may have a substantial proportionof hexamethylenetetramine therein to speed the curing. In any case the resin band should be cured to a thermo- This resin bond I will term thermorirreversible phenol-formaldehyde resin. This class of material and the manner of curing and compounding it is now well known in the abrasive art and also in other arts and therefore needs no further description. The proportions of the abrasive and of the thermo -irreversible phenol-formaldehyde resin, the grit size of the abrasive, the pore 'ty oi the annular portion 2% a a be a ied v -t n he usua limits and n ac rdance. w th h stasz c no well now the abrasive art and particularly adapted for coping wheels. These matters, therefore, need no further elucidation herein.

The layer Zia consists of and the layer Zib comprises alkyd resin. The alkyd resins are the condensation products of polyhydric alcohols and polycarboxylic acids. Any of these may be used, the most common alkyd resin being the condensation product of glycerol and phthalic anhydride. Other polyhydric alcohols W ch ca be used to make alkyd resins are, besides glycerol: penta erithritol, penta glycerol, ethylene glycol. propylene glycol, butylene glycol, trimethylomethane, 2-ethyl hexane diol. Other acids which can be used to make alkyd resins besides phthalic anhydrides are: maleic anhydride, succinic anhydride, glutaric acid, adipic acid, and tricarballylic acid.

In order to form the annular portion 20 with the layer Zia of thermoplastic resin thereunder on the center iii, the following procedure may be adopted: the steel center ii] is thoroughly cleaned on both sides of the peripheral portion i4 and on both sides of the hub portion i5 near the shoulders iii to remove grease therefrom, and this may be done by immersing these portions in a suitable grease solvent such as gasolene. These portions are then coated with a solution of thermoplastic resin. Any suitable solvent may be used, acetone, methyl alcohol and ethyl alcohol being examples. The thermoplastic resin solution is then allowed to dry at room temperature and then another coating of the solution is applied. These steps are repeated until a layer of thermoplastic resin of the required thickness is obtained. That is to say, the solution is brushed on, dried, more of the solution is brushed, dried again, still more of the solution is brushed on, dried again, and these steps are repeated over and over until the layer has been built up to the required thickness. This required thickness is not less than one thirtysecond of an inch and may be varied in accordance with the grit size of the abrasive in the annular portion 20, being greater the greater the grit size. There is, however, no upper limit to the thickness of the layer 2 id excepting that that part of the annular portion 20 outside of the layer 2 la on either side should have a thickness at least as great as that of the layer 2 la within it.

For the alkyd resins the preferred solvent is acetone.

In order to form the annular portion 20 a suitable mold can be used. A layer of a mixture of uncured phenol-formaldehyde resin and abrasive can be placed in the mold, then the center ill with the layer Zia can be placed thereon, then a further layer of resin and abrasive can be added and levelled off, the top plate of the mold can then be placed in position, the contents of the mold can then be pressed in an hydraulic press thereafter the center ill with pressed layer Zia and pressed annular portion 20 can be stripped from the mold and cured in an oven. This technique of molding, pressing and curing grinding wheels including coping wheels is now well known in the art so it need not further be described herein. Also various ways of compounding a mixture of uncured resin and abrasive are well known and need not be further described. However it is pointed out that, just prior to inserting the center i0 with the layer 2ia into the mold, the last brushing on of the solution of thermoplastic resin should be done without any subsequent drying step as this promotes adhesion of the layer Zia to the annular portion 20. The curing in an oven should be sufiicient that is to a high enough temperature and for a long enough time to convert the uncured phenol-formaldehyde resin to the thermo irreversible stage, the temperatures and times necessary to do this being also well known. During this curing the remainder of any solvent in the thermoplastic resin is driven off and the layer Zia becomes rigid and adheres firmly to the center ill but it is still slightly plastic when heated.

For the formation of the annular portion 29 with the layer Zib of thermoplastic resin there under on the center iii I may proceed as above with the following differences: a first coating of the solution of thermoplastic resin is applied and dried at room temperature. Abrasive grain, refractory grain or other inert (at the temperatures involved) granular material is coated with the thermoplastic resin and this can be done by mixing the granular material with a solution of such resin and subsequently drying to evaporate the solvent, and these steps may be repeated several times to build up a substantial layer of the resin on each granule, three repeats of the coating process being suflicient and even one such coating being adequate in many cases. The granular material can be ordinary sand such as quartz sand, or abrasive such as aluminum oxide abrasive or silicon carbide abrasive can be used. The grit size of this granular material can be varied but ordinarily should not be greater than the grit size of the abrasive in the annular portion 29; I have had good results using granular material of 60 mesh grit size for this purpose. If the granules of the granular material stick together screening or other procedure should be employed to separate the individual granules at least for the most part. The granular, refractory or abrasive material in the layer 2 lb may be properly described generically as inert material. It functions as an inert filler.

Now the steel center is brushed a second time with the solution of resin and while the coating thus produced is still in a tacky condition the center is rolled in the coated granular material above described. Then, if the thickness of the coating is not yet sufficient, the coating is air dried. Application of solution, rolling and air drying is then continued or repeated until the desired thickness of coating has been attained, but as in the previous case the last applied portion of the coating is not permitted to air dry but rather the molding operation previously described is undertaken while the coating which now constitutes the layer 2ib is still in a tacky condition. The rest of the procedure is or may be as above described. The thickness or" the layer 2 II) should also be not less than one thirtysecond of an inch and may be varied in accordance with the grit size of the abrasive in the annular portion 28, being greater the greater the grit size, and there is likewise no upper limit to the thickness of the layer 2ib excepting as stated in connection with the layer Zia.

The excellence of thermo-irreversible phenolformaldehyde resin as a bond for the manufacture of coping wheels is already known. That is to say coping wheels having the abrasive portion bonded with thermo-irreversible phenol-formaldehyde resin give superior results when measured by proper standards to coping wheels the abrasive portion of which is bonded with any other organic bond now known. However the abrasive portion, when bonded with thermo-irreversible phenol-formaldehyde resin, has frequently fractured especially when the coping wheels have been used in dry grinding. Dry grinding operations heat the abrasive portion and in so much as the steel center may be relatively cool, being a good conductor of heat, and furthermore since the coefiicient of thermal-expansion of the abrasive portion and the steel center is different, breakages have been frequent. The present invention, however, solves this difiiculty in that the plasticity of the layers 2m and 2lb is such as substantially to eliminate this cause of wheel breakage. Expansion of the annular portion 20 relative to the steel center I0 is accommodated by the layer 2 la or the layer 2 lb which, especially when heated, will deform, stretch or bend instead of breaking. Furthermore I have found that the adhesion of the layers 2m and 2|b to the steel center l0 and to the portion 20 is entirely satisfactory. Thus the invention provides a coping wheel which is highly efficient in operation, can be used in dry grinding operations, and will not readily fracture.

I have illustrated and described two practical embodiments of the invention. I now prefer the embodiment shown in Figure 3 where the layer 211) underlies the abrasive portion 20. This is for the reason that the layer 2lb is a little stronger than the layer Zia. However for many wheels the layer 2 la is adequate and it is a little simpler to make a wheel having the layer 21a than it is to make a, wheel having the layer 2 lb.

It will thus be seen that there has been provided by this invention a grinding wheel particularly of that variety known as a coping wheel in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiments above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A coping wheel comprising a steel center, an annular abrasive portion of abrasive grain bonded with thermo-irreversible phenol-forma1 dehyde resin on the periphery of said steel center, and a layer of alkyd resin between said abrasive portion and said steel center on both sides of said steel center, said layer being at least one thirtysecond of an inch thick and said annular abrasive portion outside of the layer of alkyd resin on both sides having a thickness at least as great as that of the layer of alkyd resin within it.

2. A coping wheel as claimed in claim 1 in which the layer of alkyd resin includes particles of inert material.

3. A coping wheel comprising a steel center, an annular abrasive portion of abrasive grain bonded with thermo-irreversible phenol-formaldehyde resin at least one thirty-second of an inch thick on the periphery of said steel center, and a layer of alkyd resin between said abrasive portion and said steel center on both sides of said steel center, said layer being at least one thirty-second of an inch thick and said annular abrasive portion outside of the layer of alkyd resin on both sides having a thickness at least as great as that of the layer of alkyd resin within it.

4. A coping wheel as claimed in claim 3 in which the layer of alkyd resin includes particles of inert material.

ERNEST DOUGLAS TEAGUE.

No references cited. 

1. A COPING WHEEL COMPRISING A STEEL CENTER, AN ANNULAR ABRASIVE PORTION OF ABRASIVE GRAIN BONDED WITH THERMO-IRREVERSIBLE PHENOL-FORMAL DEHYDE RESIN ON THE PERIPHERY OF SAID STEEL CENTER, AND A LAYER OF ALKYD RESIN BETWEEN SAID ABRASIVE PORTION AND SAID STEEL CENTER ON BOTH SIDES OF SAID STEEL CENTER, SAID LAYER BEING AT LEAST ONE THIRTYSECOND OF AN INCH THICK AND SAID ANNULAR ABRASIVE PORTION OUTSIDE OF THE LAYER OF ALKYD RESIN ON BOTH SIDES HAVING A THICKNESS AT LEAST AS GREAT AS THAT OF THE LAYER OF ALKYD RESIN WITHIN IT. 